磷石膏流化分解过程颗粒的黏附特性研究

发布时间：2018-05-07 06:53

  本文选题：磷石膏 + 分解　； 参考：《昆明理工大学》2017年硕士论文

【摘要】：磷石膏是工业湿法磷酸工艺生产中产生的副产物,由于其产量大,综合利用率低等问题严重影响磷酸工艺的发展和资源的浪费。针对磷石膏循环利用的实际问题,在磷石膏制硫酸联产水泥及流化实验过程中发现磷石膏粉末团聚黏附现象较为严重,所以考虑到磷石膏热分解过程的特性和反应机理,本论文结合课题组前期研究,采用两步法分解磷石膏,研究其过程反应机理和团聚黏附机理。进行了对磷石膏流化态的热态冷态黏附研究,以及SiO2对黏附团聚的影响,通过对磷石膏脱硅进而研究Si02对分解反应的影响,并探索脱硅磷石膏对水泥熟料成分的研究。本论文得到的主要研究成果如下:1.通过对磷石膏做冷态流态化实验,结果表明:常温下,磷石膏混合粉体进料量对于黏附量趋于稳定值,随着温度的升高黏附量稳定值有下降趋势;气速越大,会明显的降低颗粒的黏附程度,且随着气速增加,黏附程度趋于稳定,在现有的实验条件下,风速为2.2m/s时黏附量开始趋于稳定;在相同温度和通气速率下,粉末颗粒粒径越小越易黏附在壁面。2.磷石膏两步法热分解过程中黏附现象研究结果表明:在升温过程中粉体的黏附程度呈先降低后有所增加再减小,且颗粒的团聚现象和壁面黏附现象具有一定的一致性;在循环通气阶段,不同阶段的黏附程度也不一样,氧化阶段壁面黏附程度会有明显的下降,而当切换到还原气氛时,颗粒的黏附程度又会加重;SEM分析管壁结垢物和管道流体物的形态发现,结垢物形状大小各异,粘结情况严重;而流体物中的颗粒整体形态较为规整,呈明显的层状,表面也比较平整。分析管壁结垢物和管道流体物XRF数据发现磷石膏在流化过程中Si、Al等矿物质元素容易在壁面产生富集,并且增加壁面的黏附程度,而在循环通气反应过程中,CaO的产生会有效的破坏SiO2、Al2O3等产生的网状结构,从而有效的降低颗粒的黏附现象;3.在对不同程度脱硅的磷石膏(含Si02量分别为8.8%、4%、2%)进行黏附团聚研究过程中发现,Si02含量越低其团聚黏附程度就越小,总体随温度变化趋势基本一致。4.通过对不同程度脱硅的磷石膏(含Si02量分别为8.8%、4%、2%)进行了热分解对比和对水泥熟料指标的评价,结果表明:在热重实验中,未脱硅磷石膏失重率明显高于脱硅磷石膏,且Si02含量越低,在温度950℃下还原反应的反应程度越低;通过循环两步法分解磷石膏,未脱硅磷石膏、脱硅磷石膏(Si02量4%)和脱硅磷石膏(Si02量2%)的脱硫率分别为86.45%、75.15%和80.53%,说明一定量的去除Si02会一定程度抑制磷石膏的热分解;通过对三种磷石膏分解产物分析后,脱硅磷石膏(Si02量2%)的三个率值更加符合水泥熟料规定,且脱硅磷石膏会明显的降低硅率SM率值,增加石灰饱和系数KH,对于铝率IM影响不明显。
[Abstract]:Phosphogypsum is a by-product produced in the process of industrial wet phosphoric acid production. The development of phosphoric acid process and the waste of resources are seriously affected by its large output and low comprehensive utilization ratio. In view of the practical problems of phosphogypsum recycling, it is found that the agglomeration and adhesion of phosphogypsum powder is serious in the process of co-producing cement with sulfuric acid from phosphogypsum and fluidization, so the characteristics and reaction mechanism of phosphogypsum thermal decomposition process are considered. In this paper, the process reaction mechanism and agglomeration adhesion mechanism of phosphogypsum were studied by two-step decomposition of phosphogypsum. The hot and cold adhesion of phosphogypsum in fluidized state and the effect of SiO2 on adhesion and agglomeration were studied. The effect of Si02 on decomposition reaction was studied by desilication of phosphogypsum and the composition of cement clinker was studied. The main research results of this paper are as follows: 1. The cold fluidization experiment of phosphogypsum shows that the feed amount of phosphogypsum powder tends to be stable at room temperature, and decreases with the increase of temperature, and the gas velocity increases. The adhesion degree of particles decreased obviously with the increase of gas velocity, and the adhesion degree tended to be stable with the increase of gas velocity. Under the existing experimental conditions, the adhesion began to stabilize when the wind speed was 2.2m/s; at the same temperature and aeration rate, The smaller the particle size is, the easier it is to adhere to the wall. The results show that the adhesion degree of the powder decreases first and then increases and then decreases during the process of pyrolysis of phosphogypsum, and the agglomeration of particles is consistent with the phenomenon of wall adhesion to some extent. In the stage of circulatory ventilation, the adhesion degree of different stages is also different, the adhesion degree of wall surface in oxidation stage will decrease obviously, but when switching to reducing atmosphere, The adhesion degree of particles will aggravate the SEM analysis of the morphology of pipe wall fouling and pipe fluid. It is found that the shape of the fouling is different and the adhesion is serious, while the whole shape of the particles in the fluid is more regular and obviously layered. The surface is also relatively flat. By analyzing the XRF data of pipe wall fouling and pipe fluid, it is found that Si-Al and other mineral elements are easily enriched on the wall during fluidization, and the adhesion degree of the wall is increased. However, in the process of circulating ventilation reaction, the formation of Cao can effectively destroy the network structure produced by Sio _ 2O _ 2O _ 3, and thus effectively reduce the adhesion phenomenon of particles / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 / Al _ 2O _ 3 system. In the study of adhesion and agglomeration of phosphogypsum with different degree of desilication (containing Si02 content of 8.8% and 4%), it was found that the lower the content of SiO2 was, the smaller the degree of agglomeration adhesion was, and the overall trend of agglomeration was basically consistent with the change of temperature. The pyrolysis and comparison of phosphogypsum with different degree of desilication (including Si02 content of 8.8%) and evaluation of cement clinker index are carried out. The results show that the weight loss rate of undesilication phosphorous gypsum is obviously higher than that of desilication phosphorous gypsum in thermogravimetric experiment. The lower the content of Si02, the lower the degree of reduction at 950 鈩，

本文编号：1855858